codertimo · wanghesong2019 · Jan 20, 2023 · Jan 28, 2023 · Jan 28, 2023 · Jan 28, 2023
diff --git a/BERT-pytorch b/BERT-pytorch
diff --git a/README.md b/README.md
@@ -1,120 +1,20 @@
-# BERT-pytorch
+# BERT-pytorch学习心得
+在2023年的2月中旬的凌晨2点，我要结束对BERT-pytorch项目的学习了，这是注册github账号之后第1次相对认真系统的学习一个开源项目，从寒假前夕开始，持续直到现在，坚持下来了离开之前，啰嗦2句，以作纪念！
+## 1.经验
+- 根据代码，结合bert论文，基本掌握了bert的真面目：包括词典构建和token随机替换，句子对随机采样的dataset模块、基于transformer编码器的encoder架构的modeling模块、包括loss计算和梯度下降的trainner模块；
+- 在代码学习的过程中，掌握了git基本操作，github的使用习惯(自己的注释都合并到了master分支)和常见pytorch API用法；
+- 开源项目学习最好结合论文看，这样就将理论和实践结合起来了，当然最好是能灌入数据跑起来
 
-[![LICENSE](https://img.shields.io/github/license/codertimo/BERT-pytorch.svg)](https://github.com/codertimo/BERT-pytorch/blob/master/LICENSE)
-![GitHub issues](https://img.shields.io/github/issues/codertimo/BERT-pytorch.svg)
-[![GitHub stars](https://img.shields.io/github/stars/codertimo/BERT-pytorch.svg)](https://github.com/codertimo/BERT-pytorch/stargazers)
-[![CircleCI](https://circleci.com/gh/codertimo/BERT-pytorch.svg?style=shield)](https://circleci.com/gh/codertimo/BERT-pytorch)
-[![PyPI](https://img.shields.io/pypi/v/bert-pytorch.svg)](https://pypi.org/project/bert_pytorch/)
-[![PyPI - Status](https://img.shields.io/pypi/status/bert-pytorch.svg)](https://pypi.org/project/bert_pytorch/)
-[![Documentation Status](https://readthedocs.org/projects/bert-pytorch/badge/?version=latest)](https://bert-pytorch.readthedocs.io/en/latest/?badge=latest)
+## 2.教训
+- 代码逐行看了，也搭建了bert-pytorch环境，但是没有结合数据去运行查看结果，故调参经验并没有增加
+- 项目学习没有指定里程碑时间表，拖沓
+- 后续的开源项目学习，一定要结合数据，运行起来
+- 本来想好好写一篇readme，但是到头有泄气了。
 
-Pytorch implementation of Google AI's 2018 BERT, with simple annotation
+---
+# bert理解记录
 
-> BERT 2018 BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding
-> Paper URL : https://arxiv.org/abs/1810.04805
+## 20230213：今天和大华同事明浩讨论了bert的embedding部分：由token到初始化的embedding向量是怎么实现的？他认为初始化的embedding向量会参与到训练学习中，但是晚上我又看了下该项目，发现本项目的embedding模块只是承担着token的随机初始化过程，之后就会进到attention模块，先线性投影成querey,key,value之后就开始了注意力机制的计算；由此可以认为embedding模块还只是数据预处理的一部分，是不会参与到训练中的；
 
+另外一个问题是为什么可以随机初始化embedding？我认为主要是token的索引就是随机的(现到先得)，也就是说不管是token的index，还是初始的embedding向量，只要固定好key-value关系即可，不含任何的语义信息；这样就能圆回来了：如果初始化的embedding是模型参数，参与到学习训练，就破环了key-value关系的确定性；
 
-## Introduction
-
-Google AI's BERT paper shows the amazing result on various NLP task (new 17 NLP tasks SOTA), 
-including outperform the human F1 score on SQuAD v1.1 QA task. 
-This paper proved that Transformer(self-attention) based encoder can be powerfully used as 
-alternative of previous language model with proper language model training method. 
-And more importantly, they showed us that this pre-trained language model can be transfer 
-into any NLP task without making task specific model architecture.
-
-This amazing result would be record in NLP history, 
-and I expect many further papers about BERT will be published very soon.
-
-This repo is implementation of BERT. Code is very simple and easy to understand fastly.
-Some of these codes are based on [The Annotated Transformer](http://nlp.seas.harvard.edu/2018/04/03/attention.html)
-
-Currently this project is working on progress. And the code is not verified yet.
-
-## Installation
-```
-pip install bert-pytorch
-```
-
-## Quickstart
-
-**NOTICE : Your corpus should be prepared with two sentences in one line with tab(\t) separator**
-
-### 0. Prepare your corpus
-```
-Welcome to the \t the jungle\n
-I can stay \t here all night\n
-```
-
-or tokenized corpus (tokenization is not in package)
-```
-Wel_ _come _to _the \t _the _jungle\n
-_I _can _stay \t _here _all _night\n
-```
-
-
-### 1. Building vocab based on your corpus
-```shell
-bert-vocab -c data/corpus.small -o data/vocab.small
-```
-
-### 2. Train your own BERT model
-```shell
-bert -c data/corpus.small -v data/vocab.small -o output/bert.model
-```
-
-## Language Model Pre-training
-
-In the paper, authors shows the new language model training methods, 
-which are "masked language model" and "predict next sentence".
-
-
-### Masked Language Model 
-
-> Original Paper : 3.3.1 Task #1: Masked LM 
-
-```
-Input Sequence  : The man went to [MASK] store with [MASK] dog
-Target Sequence :                  the                his
-```
-
-#### Rules:
-Randomly 15% of input token will be changed into something, based on under sub-rules
-
-1. Randomly 80% of tokens, gonna be a `[MASK]` token
-2. Randomly 10% of tokens, gonna be a `[RANDOM]` token(another word)
-3. Randomly 10% of tokens, will be remain as same. But need to be predicted.
-
-### Predict Next Sentence
-
-> Original Paper : 3.3.2 Task #2: Next Sentence Prediction
-
-```
-Input : [CLS] the man went to the store [SEP] he bought a gallon of milk [SEP]
-Label : Is Next
-
-Input = [CLS] the man heading to the store [SEP] penguin [MASK] are flight ##less birds [SEP]
-Label = NotNext
-```
-
-"Is this sentence can be continuously connected?"
-
- understanding the relationship, between two text sentences, which is
-not directly captured by language modeling
-
-#### Rules:
-
-1. Randomly 50% of next sentence, gonna be continuous sentence.
-2. Randomly 50% of next sentence, gonna be unrelated sentence.
-
-
-## Author
-Junseong Kim, Scatter Lab (codertimo@gmail.com / junseong.kim@scatterlab.co.kr)
-
-## License
-
-This project following Apache 2.0 License as written in LICENSE file
-
-Copyright 2018 Junseong Kim, Scatter Lab, respective BERT contributors
-
-Copyright (c) 2018 Alexander Rush : [The Annotated Trasnformer](https://github.com/harvardnlp/annotated-transformer)
diff --git a/README_back.md b/README_back.md
@@ -0,0 +1,120 @@
+# BERT-pytorch
+
+[![LICENSE](https://img.shields.io/github/license/codertimo/BERT-pytorch.svg)](https://github.com/codertimo/BERT-pytorch/blob/master/LICENSE)
+![GitHub issues](https://img.shields.io/github/issues/codertimo/BERT-pytorch.svg)
+[![GitHub stars](https://img.shields.io/github/stars/codertimo/BERT-pytorch.svg)](https://github.com/codertimo/BERT-pytorch/stargazers)
+[![CircleCI](https://circleci.com/gh/codertimo/BERT-pytorch.svg?style=shield)](https://circleci.com/gh/codertimo/BERT-pytorch)
+[![PyPI](https://img.shields.io/pypi/v/bert-pytorch.svg)](https://pypi.org/project/bert_pytorch/)
+[![PyPI - Status](https://img.shields.io/pypi/status/bert-pytorch.svg)](https://pypi.org/project/bert_pytorch/)
+[![Documentation Status](https://readthedocs.org/projects/bert-pytorch/badge/?version=latest)](https://bert-pytorch.readthedocs.io/en/latest/?badge=latest)
+
+Pytorch implementation of Google AI's 2018 BERT, with simple annotation
+
+> BERT 2018 BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding
+> Paper URL : https://arxiv.org/abs/1810.04805
+
+
+## Introduction
+
+Google AI's BERT paper shows the amazing result on various NLP task (new 17 NLP tasks SOTA), 
+including outperform the human F1 score on SQuAD v1.1 QA task. 
+This paper proved that Transformer(self-attention) based encoder can be powerfully used as 
+alternative of previous language model with proper language model training method. 
+And more importantly, they showed us that this pre-trained language model can be transfer 
+into any NLP task without making task specific model architecture.
+
+This amazing result would be record in NLP history, 
+and I expect many further papers about BERT will be published very soon.
+
+This repo is implementation of BERT. Code is very simple and easy to understand fastly.
+Some of these codes are based on [The Annotated Transformer](http://nlp.seas.harvard.edu/2018/04/03/attention.html)
+
+Currently this project is working on progress. And the code is not verified yet.
+
+## Installation
+```
+pip install bert-pytorch
+```
+
+## Quickstart
+
+**NOTICE : Your corpus should be prepared with two sentences in one line with tab(\t) separator**
+
+### 0. Prepare your corpus
+```
+Welcome to the \t the jungle\n
+I can stay \t here all night\n
+```
+
+or tokenized corpus (tokenization is not in package)
+```
+Wel_ _come _to _the \t _the _jungle\n
+_I _can _stay \t _here _all _night\n
+```
+
+
+### 1. Building vocab based on your corpus
+```shell
+bert-vocab -c data/corpus.small -o data/vocab.small
+```
+
+### 2. Train your own BERT model
+```shell
+bert -c data/corpus.small -v data/vocab.small -o output/bert.model
+```
+
+## Language Model Pre-training
+
+In the paper, authors shows the new language model training methods, 
+which are "masked language model" and "predict next sentence".
+
+
+### Masked Language Model 
+
+> Original Paper : 3.3.1 Task #1: Masked LM 
+
+```
+Input Sequence  : The man went to [MASK] store with [MASK] dog
+Target Sequence :                  the                his
+```
+
+#### Rules:
+Randomly 15% of input token will be changed into something, based on under sub-rules
+
+1. Randomly 80% of tokens, gonna be a `[MASK]` token
+2. Randomly 10% of tokens, gonna be a `[RANDOM]` token(another word)
+3. Randomly 10% of tokens, will be remain as same. But need to be predicted.
+
+### Predict Next Sentence
+
+> Original Paper : 3.3.2 Task #2: Next Sentence Prediction
+
+```
+Input : [CLS] the man went to the store [SEP] he bought a gallon of milk [SEP]
+Label : Is Next
+
+Input = [CLS] the man heading to the store [SEP] penguin [MASK] are flight ##less birds [SEP]
+Label = NotNext
+```
+
+"Is this sentence can be continuously connected?"
+
+ understanding the relationship, between two text sentences, which is
+not directly captured by language modeling
+
+#### Rules:
+
+1. Randomly 50% of next sentence, gonna be continuous sentence.
+2. Randomly 50% of next sentence, gonna be unrelated sentence.
+
+
+## Author
+Junseong Kim, Scatter Lab (codertimo@gmail.com / junseong.kim@scatterlab.co.kr)
+
+## License
+
+This project following Apache 2.0 License as written in LICENSE file
+
+Copyright 2018 Junseong Kim, Scatter Lab, respective BERT contributors
+
+Copyright (c) 2018 Alexander Rush : [The Annotated Trasnformer](https://github.com/harvardnlp/annotated-transformer)
diff --git a/bert_pytorch/dataset/dataset.py b/bert_pytorch/dataset/dataset.py
@@ -15,32 +15,36 @@ def __init__(self, corpus_path, vocab, seq_len, encoding="utf-8", corpus_lines=N
         self.encoding = encoding
 
         with open(corpus_path, "r", encoding=encoding) as f:
-            if self.corpus_lines is None and not on_memory:
+            #读取预料库后分下面2种情况处理：
+            if self.corpus_lines is None and not on_memory: #如果不将语料库直接加载到内存，则需先确定语料库行数
                 for _ in tqdm.tqdm(f, desc="Loading Dataset", total=corpus_lines):
                     self.corpus_lines += 1
 
             if on_memory:
-                self.lines = [line[:-1].split("\t")
-                              for line in tqdm.tqdm(f, desc="Loading Dataset", total=corpus_lines)]
-                self.corpus_lines = len(self.lines)
+                #数据集全部加载到内存，语料库解析成list类型的self.liines属性
+                self.lines = [line[:-1].split('\t')
+                              for line in tqdm.tqdm(f, desc="Loading Dataset", total=corpus_lines)] #对预料库每行根据\t字符分成2个sentence               
+                self.corpus_lines = len(self.lines) #获取语料库行数
 
-        if not on_memory:
+        if not on_memory: 
             self.file = open(corpus_path, "r", encoding=encoding)
             self.random_file = open(corpus_path, "r", encoding=encoding)
-
+            #错位抽取负样本，作用是什么?
             for _ in range(random.randint(self.corpus_lines if self.corpus_lines < 1000 else 1000)):
                 self.random_file.__next__()
 
     def __len__(self):
         return self.corpus_lines
 
     def __getitem__(self, item):
-        t1, t2, is_next_label = self.random_sent(item)
-        t1_random, t1_label = self.random_word(t1)
-        t2_random, t2_label = self.random_word(t2)
+        #魔术方法__getitem__的定义，功能令类的实例对象向list那样根据索引item取值
+        #BERTDataset类实例化返回的bert对象均会进行Next Sentence操作和Masked LM操作
+        t1, t2, is_next_label = self.random_sent(item) #Next Sentence操作
+        t1_random, t1_label = self.random_word(t1) #Masked LM操作, 其中t1_label表示t1各个位置被masked的类别索引，参看vocab.py中Vocab类的初始化定义
+        t2_random, t2_label = self.random_word(t2) 
 
         # [CLS] tag = SOS tag, [SEP] tag = EOS tag
-        t1 = [self.vocab.sos_index] + t1_random + [self.vocab.eos_index]
+        t1 = [self.vocab.sos_index] + t1_random + [self.vocab.eos_index] #论文Figure2
         t2 = t2_random + [self.vocab.eos_index]
 
         t1_label = [self.vocab.pad_index] + t1_label + [self.vocab.pad_index]
@@ -50,7 +54,7 @@ def __getitem__(self, item):
         bert_input = (t1 + t2)[:self.seq_len]
         bert_label = (t1_label + t2_label)[:self.seq_len]
 
-        padding = [self.vocab.pad_index for _ in range(self.seq_len - len(bert_input))]
+        padding = [self.vocab.pad_index for _ in range(self.seq_len - len(bert_input))] #最大长度和实际长度之差就是需要padding的位置数量
         bert_input.extend(padding), bert_label.extend(padding), segment_label.extend(padding)
 
         output = {"bert_input": bert_input,
@@ -61,12 +65,15 @@ def __getitem__(self, item):
         return {key: torch.tensor(value) for key, value in output.items()}
 
     def random_word(self, sentence):
+        #sentence转换成sentence中的token在token-index词典中对应的index
         tokens = sentence.split()
-        output_label = []
+        output_label = [] #该列表只存0和非0数字，0表示对应位置的token属于85%没被替换的，非0数字是对应位置的token在被mask处理前的vocab中对应的index
 
         for i, token in enumerate(tokens):
             prob = random.random()
+            #BERT随机选择15%的tokens进行mask
             if prob < 0.15:
+                #对于随机选择的15%的tokens，再做一次随机
                 prob /= 0.15
 
                 # 80% randomly change token to mask token
@@ -77,26 +84,27 @@ def random_word(self, sentence):
                 elif prob < 0.9:
                     tokens[i] = random.randrange(len(self.vocab))
 
-                # 10% randomly change token to current token
+                # 10% doesn't change current token
                 else:
                     tokens[i] = self.vocab.stoi.get(token, self.vocab.unk_index)
 
                 output_label.append(self.vocab.stoi.get(token, self.vocab.unk_index))
 
             else:
-                tokens[i] = self.vocab.stoi.get(token, self.vocab.unk_index)
+                tokens[i] = self.vocab.stoi.get(token, self.vocab.unk_index) #未被masked的词，用其在vocab中真正的index填充
+                #具体地，self.vocab.unk_index=1，上句相当于从stoi token-index字典
                 output_label.append(0)
 
         return tokens, output_label
 
     def random_sent(self, index):
-        t1, t2 = self.get_corpus_line(index)
-
-        # output_text, label(isNotNext:0, isNext:1)
+        t1, t2 = self.get_corpus_line(index)        
+        # for sentence A and B, 50% of the time B is the actual next sentence that follows A(labeled as NotNext)
+        # and for 50% of the time it is a random sentence from the corpus(labeled as NotNext)
         if random.random() > 0.5:
-            return t1, t2, 1
+            return t1, t2, 1 #1表示isNext
         else:
-            return t1, self.get_random_line(), 0
+            return t1, self.get_random_line(), 0 #0表示isNotNext
 
     def get_corpus_line(self, item):
         if self.on_memory:
@@ -122,4 +130,4 @@ def get_random_line(self):
             for _ in range(random.randint(self.corpus_lines if self.corpus_lines < 1000 else 1000)):
                 self.random_file.__next__()
             line = self.random_file.__next__()
-        return line[:-1].split("\t")[1]
+        return line[:-1].split("\t")[1]